1. Field of the Invention
The present invention relates to a film image processing apparatus for converting an image recorded on a film such as a microfilm, into electrical image information signals.
2. Description of the Prior Art
There are already known apparatus, such as facsimile or digital copier, in which an image of a document or a photograph is photoelectrically read by an image sensor and the obtained image information is processed in the form of electrical signals. Such electrical handling of image enables to easily achieve complex image processing which has not been possible in the prior art.
On the other hand, microfilms are widely employed for recording documents and drawings in order to reduce the storage space therefor. Thus microfilmed image has been utilized for visual monitoring through projection onto a screen, or for hard copy preparation through projection onto a photosensitive paper.
It is however recently required to read image information recorded on a microfilm by optically projecting said image and scanning said image on the image plane thereof by means of a one- or two-dimensional photoelectric image sensor.
Such requirement occurs for example in case of electrically sharpening an unclear microfilmed image, or storing a microfilmed image into a recently developed image file utilizing an optical disk or a magnetic disk.
The image information signals, obtained from an image reading apparatus for photoelectrically reading a microfilmed image, are used for example for obtaining a hard copy in a digital printer such as a laser beam printer or an ink jet printer, providing a display on a display unit such as a cathode ray tube or a liquid crystal device, or for storage in a high-density memory such as an optical disk for subsequent image processing.
However, the reading of microfilmed image is somewhat different in nature from conventional image reading for example in a digital copier. More specifically, there may result an incorrect image reading with the image sensor if the microfilm transport to the image reading position is inaccurate, thus eventually giving rise to a partially lacking image or the recording of an unnecessary image part, in the image reproduction. Also, in document reading, the size of document is usually defined by a standardized format, or, it is relatively easy to automatically recognize the size and position of the document and accordingly control the image reading operation. On the other hand, in microfilm reading, such automatic recognition of the size and position of the recorded image, since the distinction between the recorded image and the surrounding substrate area is quite difficult.
Even in case of using the microfilm of a particular format, such as 16 mm roll microfilm, the images recorded thereon may have various sizes because of variable image magnifications at microfilming, and this fact increases the difficulty in image reading.
Also in case of printing the image read from a microfilm, the printed image may become partially lacking unless an appropriate printing sheet is loaded in the printer. Naturally such inconvenience will not result if the operator of such apparatus always pays attention to the size of the printing sheet, such confirmation is rather tedious and tends to be forgotten in the daily work.
Such drawback is partly derived from a fact that the operator is unable to immediately imagine the manner of image reproduction, since the image on the microfilm is in a reduced size and has to be enlarged for printing.
Furthermore, it is often desirable to delete an unnecessary part in the image or to extract only a desired part thereof at the image reproduction, and, in such case, the designation of an image area should desirably be easily achieved. An enlarged print of an extracted image allows more detailed observation of image, but the operator is unable to judge an appropriate image magnification because the image on the microfilm is reduced in size as mentioned above. If an inappropriate image magnification is selected, the obtained image may not be properly accommodated in the printing sheet.
The above-mentioned drawbacks are not limited to the case of microfilm but also exist in reading other films such as 35 mm films or X-ray films.